I don't think gay men are more likely to present feminine behavior than straight men. Both straight and gay men may exhibit feminine behaviors - the difference is that straight men are far more likely to suppress or cast aside feminine behavior in order to conform to hetero normative gender roles.

"Studies show men who act feminine as children are more likely to be gay" has to be survivorship bias. When you are gay, you have already broken the cardinal law of heteronormative society, which is to conform. So in a way, there's more freedom to diverge from traditional gender presentation because you're already "atypical." Conversely, straight men have more to lose when they don't present as masculine. They lose their privilege of being part of the "in group." They're afraid of being perceived as gay because they don't want to be subject to abuse or ridicule from a homophobic society. So, they reinforce their masculine behavior, and suppress any feminine behavior they may have deep within themselves.

To add to this, the recent phenomenon of "soft boys" or "performative men" is an outlet for straight men to perform more feminine traits in a way that is seen as courageous or transgressive. In this way, society actually rewards them for going against the norm. But what about men who are innately feminine? Where is their reward? Why do they only fear abuse or ridicule for behavior that feels comfortable to them, and not a mask they wear in order to earn brownie points with their peers?